Elimination of neutrons from nuclear reactions in a reactor, in particular clean laser boron-11 fusion without secondary contamination

ABSTRACT

The invention relates to a method for eliminating neutrons from fission, fusion or aneutronic nuclear reactions in a reactor, in particular in a laser-driven nuclear fusion reactor which operates with hydrogen and the boron-11 isotope, in which method at least some moderated neutrons are made to undergo a nuclear reaction with tin. As a result of the nuclear reactions with tin, the neutrons convert the tin nuclei into stable nuclei having a higher atomic weight resulting from neutron capture. The invention also relates to a reactor which is designed for energy conversion by means of fission, fusion or aneutronic nuclear reactions and for generating electric energy, wherein the reactor contains a neutron elimination device which contains tin and is arranged such that at least some moderated neutrons are made to undergo a nuclear reaction with the tin.

This application is a division of U.S. patent application Ser. No.16/766,817, filed May 26, 2020, which is a U.S. National PhaseApplication of PCT/EP2018/082520, filed Nov. 26, 2018, which claimspriority from 10 2017 010 927.3, filed Nov. 27, 2017, the contents ofwhich applications are incorporated herein by reference in theirentireties for all purposes

TECHNICAL FIELD

The invention relates to a method for the elimination of neutrons fromfission, fusion or aneutronic nuclear reactions in a reactor, inparticular for the elimination of neutrons from fusion reactions in anuclear fusion reactor, such as a laser-driven nuclear fusion reactoroperated with hydrogen and the boron isotope 11. The invention alsorelates to a nuclear reactor, in particular a laser nuclear fusionreactor, which is arranged for the generation of electrical energy bylaser-based fusion of protons with the boron isotope 11. Applications ofthe invention exist in the generation of electrical energy.

TECHNICAL BACKGROUND

When explaining the state of the art, reference is made to the followingpublications:

-   [1] WO 2015/144190 A1;-   [2] H. Hora, G. Korn, L. Giuffrida, D. Margarone, A. Picciotto, J.    Krasa, K. Jungwirth, J. Ullschmied, P. Lalousis, S. Eliezer, G. H.    Miley, S. Moustaizis and G. Mourou, Fusion energy using avalanche    increased boron reactions for block ignition by ultrahigh power    picosecond laser pulses. Laser and Particle Beams. 33, 607-619    (2015);-   [3] H. Hora, S. Eliezer, N. Nissim and P. Lalousis. Non-thermal    Laser Driven Plasma-Blocks for Proton Boron Avalanche Fusion as    Direct Drive Option. Matter and Radiation at Extremes (Elsevier) 2,    177-189 (2017);-   [4] H. Hora, Comment on Finkel-Report: Australian Government    Commission headed by Chief Scientist Dr Alan Finkel 2017 on Energy    (Report der Academy of Technological Science and Engineering (ATSE)    Melbourne, Symposium Sydney Jan. 11, 2017);-   [5] H. Hora Laser Plasma Physics 2nd ed 2016, SPIE Book Bellingham    Wash., USA; and-   [6] Shalom Eliezer, Heinrich Hora, Georg Korn, Noaz Nissim and José    Maria Martinez-Val. Avalanche proton-boron fusion based on elastic    nuclear collisions. Physics of Plasmas 23, 050704 (2016).

It is well known that a clean production of electrical energy avoidspollution of the earth's atmosphere by the combustion of carbonaceousfuel or the production of radioactive waste from nuclear fissionreactors. A clean electric power generator is described in [1],primarily using the neutron-free fusion reaction of hydrogen and theisotope 11 of boron (HB11 fusion) by a non-thermal ignition with extremelaser pulses. The plasma acceleration for ignition is achieved bynon-linear forces of the electromagnetic field of the laser pulses,combined with ultra-high magnetic fields to hold the reaction volume ofthe nuclear fusion together.

While HB11 fusion is absolutely neutron-free, a secondary reactionoccurs by the primary helium nuclei (alpha particles) by reacting withthe boron-11 nuclei present in the fuel, including a production ofharmless, stable nitrogen and a neutron. This reaction is weak and isless than 0.1% of the number of HB11 reactions, and the energy of theneutrons of 0.85 MeV produced is comparatively very low. These neutronsdecay with a half-life of 14 minutes into an electron and a proton.Until this decay, however, the neutrons can contribute in a dangerousway to radioactive waste. Because neutrons have no electrical charge,they can come close to and penetrate other atomic nuclei (so-calledneutron capture), whereby a normally harmless stable atomic nucleusbecomes a radioactive nucleus.

The HB11 reactor can practically be realized with available techniques,using petawatt laser pulses with high repetition rates. Boron fusion hasalways been considered particularly difficult and practicallyimpossible. However, the goal of a “Clean Energy Target” solutionwithout neutrons and without radioactive waste, as introduced by Finkel,always was of great interest (see [4]). Measurements of the HB11reaction as the basis of the HB11 nuclear fusion reactor described belowhave so far been achieved with lasers (Belyaev et al. 2005 in Moscow,Labaune et al. 2013 in Paris and Picciotto et al. 2014 in Prague).However, based on the completely neutron-free reaction of hydrogen withboron-11 as the realization of the goal of an absolutely clean energysource, the mentioned limitation from a contaminating secondary reactionis known. The HB11 reaction, which is completely clean in the firststep, produces the clean helium nuclei of alpha particles, but thesereact with the boron-11 nuclei in the fusion fuel and convert theboron-11 nuclei into stable nitrogen nuclei by splitting off anon-energy-rich neutron.

Radiation risks from neutrons or the consequences of the interaction ofneutrons with atoms in reactor parts or in the vicinity of the reactoralso exist in other nuclear reactions in fission, fusion or other aneutron nuclear reactors.

OBJECTIVE OF THE INVENTION

An objective of the invention is to provide an improved method foreliminating neutrons from fission, fusion or aneutronic nuclearreactions in a reactor, which avoids disadvantages and limitations ofconventional methods and which in particular allows a reduction of thenumber of neutrons in the vicinity of the reactor and/or a reduction ofinteractions of neutrons with atoms in reactor parts or in the vicinityof the reactor. A further objective of the invention is to provide animproved nuclear reactor, in particular a nuclear fusion reactor, withwhich disadvantages and limitations of conventional techniques areavoided and which is characterized in particular by a reduction of thenumber of neutrons and neutron-atom interactions.

BRIEF SUMMARY OF THE INVENTION

These objectives are solved by a neutron elimination method and anuclear reactor of the invention.

According to a first general aspect of the invention, the aboveobjective is solved by a method for the elimination of neutrons fromfission, fusion or aneutronic nuclear reactions in a reactor in which atleast partially moderated neutrons are made to nuclearly react with tin.

According to a second general aspect of the invention, the aboveobjective is solved by a reactor which is configured for energyconversion by means of fission, fusion or aneutronic nuclear reactionsand for the generation of electric energy, the reactor comprising aneutron elimination device including tin and being arranged such thatmoderated neutrons are at least partially brought to nuclear reactionswith the tin.

A third general aspect of the invention is the use of tin foreliminating neutrons generated as a result of fission, fusion oraneutronic nuclear reactions in a reactor. The neutrons produced by theprimary reaction or by secondary reactions in the reactor are wholly orpartly absorbed by tin, in particular in purely metallic or compoundform (e.g. alloy).

The invention is based on the knowledge that neutron capture, whichoften produces a radioactively radiating nucleus from a harmless stableatomic nucleus, is uncritical for those elements which have as manydifferent stable isotopes as possible. Among these elements, tin hasproven to be particularly advantageous because of its high effectivecross section.

The elimination of radiation-hazardous neutrons by their limitedlifetime of 14 minutes half-life until decay into non-radioactivelydamaging electrons and protons (hydrogen nuclei) can be applied to allenergy-producing nuclear reactors with fission or fusion and inparticular to the following example of aneutronic nuclear fusion bymeans of “Laser Boron Fusion”. This is the “Clean Energy Target” forinnovations, which goes far beyond the previous initiatives of“renewable energy”.

Preferably, by nuclear reactions with tin, neutrons transform tin nucleiby neutron capture into stable nuclei with a higher atomic weight.Advantageously, no radiating residues remain.

A laser-driven nuclear fusion reactor is particularly preferred, whichworks with hydrogen and the boron isotope 11 primarily without producingneutrons, whereby secondary neutrons produced by the reaction of alphaparticles with boron isotope 11 are at least partially eliminated. Asstated in [2], the number of unwanted neutrons, in particular in theHB11 nuclear fusion reactor, is comparatively very low and their energyrelatively low. The reactor is preferably a laser-driven nuclear fusionreactor, which has a magnetic field device configured to hold a fusionfuel and to generate a magnetic field with a field strength greater thanor equal to 1 kT in a cylinder-shaped reaction space, a fusion pulselaser source configured to emit fusion laser pulses, whose pulseduration is less than 10 ps and whose power is more than 1 petawatt andis configured to initiate nuclear fusion in the fusion fuel, and anenergy conversion means for converting the energy released from thegenerated nuclei during nuclear fusion into power plant output, whereinthe neutron elimination device is arranged as wall material of thereactor. The neutron elimination device preferably surrounds the reactorspace of the laser-driven nuclear fusion reactor on all sides.

The laser-driven nuclear fusion reactor preferably has the properties ofthe nuclear fusion reactor described in [1]. Accordingly, WO 2015/144190A1 is incorporated by reference in the present description of theinvention with respect to the details of the construction of the nuclearfusion reactor and its operation, in particular with respect to thegeneration of the magnetic field for holding a fusion fuel and thedesign of the energy conversion device.

Advantageously, tin can be used in various forms to eliminate neutrons.According to a first variant, metallic tin is used, through which theneutrons produced primarily or subsequently during the nuclear reactionfly. Preferably, the neutron elimination device consists of pure tin. Inthis case, advantages can result from the high effectiveness of theneutron elimination. Alternatively, at least one compound of tin, e.g.at least one tin alloy, is used. In this case, advantages may resultfrom the fact that the at least one tin compound can be used as amaterial for the manufacture of reactor parts, e.g. reactor walls.

Particularly preferred, the metallic tin or the at least one tincompound is used as wall material of the reactor. In other words,reactor walls surrounding a reactor space of the reactor may consist ofthe metallic tin or the at least one tin compound or be made layeredwith a support and a layer of the metallic tin or the at least one tincompound.

The range of fast neutrons, which normally travel long distances throughmaterials, can be substantially reduced if they have elastic collisionswith, for example, protons or deuterons. This so-called thermalizationof fast neutrons can be done e. g. with water or heavy water or withsolid or liquid paraffin of sufficient thickness. Accordingly, accordingto another preferred embodiment of the invention, it is provided thatthe neutrons lower their energy by elastic collisions when passingthrough a thermalizing liquid. Preferably, a thermalization device isprovided which contains a thermalization liquid and which is arranged toreduce the energy of the neutrons by elastic collisions when passingthrough the thermalization liquid. Preferably, the thermalizing liquidincludes protons, deuterons, carbon, oxygen and/or components thereofand/or metallic tin particles of more than one nanometer in size.

Advantageously, the thermalization device can fulfil a further functionbesides the deceleration function and can also be arranged as a heatexchanger for the transfer of energy, which is generated duringoperation of the reactor, to a heat exchange medium. During operation ofthe reactor, the thermalization liquid is heated and used for heattransfer to the heat exchange medium.

According to another preferred embodiment of the invention, the tinincludes isotopes 114 to 119 and, with less than 0.01%, isotopes 112 and122. This embodiment minimizes the probability of undesired nuclearreactions. Particularly preferred, the tin contains the isotopes 114,115 and/or 116 in at least 99.9% purity each or mixtures thereof.

Particularly preferred, the neutron elimination device is configured insuch a way that on the outer wall of the reactor, including a shieldinglayer, there are less neutron densities during power generationoperation than are prescribed by a predetermined limit concentration forenvironmentally clean operation. This limit concentration results fromestimates known per se from the literature.

In the following, essential features of the present invention aresummarized:

1) Elimination of neutrons from fission, fusion and aneutronic fusionreactions, characterized in that at least partially moderated neutronsare brought to nuclear reactions with tin;

2) Elimination of neutrons from fission, fusion and aneutronic fusionreactions according to 1), characterized in that the neurons movethrough solid metallic tin or compounds;

3) Elimination of neutrons from fission, fusion and aneutronic fusionreactions according to 1) to 2), characterized in that metallic tin isused as the wall material of the reactor;

4) Elimination of neutrons from fission, fusion and aneutronic fusionreactions according to 1) to 3), characterized in that the neutronsreduce their energy by elastic collisions when passing through liquidscontaining protons, or deuterons, or carbon, or oxygen or componentsthereof;5) Elimination of neutrons from fission, fusion and aneutronic fusionreactions according to 1) to 4), characterized in that the liquidscontain metallic tin particles of more than nanometer size.

6) Elimination of neutrons from fission, fusion and aneutronic fusionreactions according to 1) to 5), characterized in that tin contains theisotopes 112 and 122 in less than 0.01% in addition to the isotopes 114to 119.

7) Elimination of neutrons from fission, fusion and aneutronic fusionreactions according to 1) to 5), characterized in that the tin usedcontains the isotopes 114, 115 and/or 116 in each case in at least 99.9%purity or mixtures thereof;

8) Elimination of neutrons from fission, fusion and aneutronic fusionreactions according to 1) to 7), characterized in that on the outer wallof the reactor including the shielding layer during operation of thepower generation there are less neutron densities than are prescribed bythe limit concentration for environmentally clean operation.

BRIEF DESCRIPTION OF THE FIGURES

Further details and advantages of the invention are explained below withreference to the attached drawings, which show in:

FIG. 1: a schematic illustration of an embodiment of the inventionnuclear fusion reactor according to the invention; and

FIG. 2: a schematic illustration of a nuclear fusion reactor with athermalization device.

PREFERRED EMBODIMENTS OF THE INVENTION

Features of preferred embodiments of the invention are described below,primarily with reference to a nuclear fusion reactor as defined in [1].However, the invention is not limited to this nuclear fusion reactor,but is also applicable to other reactors which produce neutrons duringoperation. Details of the nuclear fusion reactor, such as the details oflaser pulse sources, the physical principles of the HB11 reaction, theconnection of the fusion reactor with further components of a powerplant, in particular for the preparation and supply of the fusion fuel,for the control of the fusion reactor, for the protection of theenvironment against thermal influences and/or electric fields, are notdescribed, since they can be realized by a skilled person, based on theknowledge of known fusion and plasma physics and conventional powerplant technology, depending on the concrete application conditions ofthe invention. Reference is made by example to a fusion reactor with asingle reaction chamber. However, the invention is not limited to thisdesign. Rather, a fusion reactor can be provided with a plurality ofreaction chambers, each with a magnetic field device for holding fusionfuel. The reaction chambers can be operated sequentially alternately insuch a way that a continuous or quasi-continuous generation ofelectrical energy is possible.

The laser-driven nuclear fusion reactor described in [1] to [3] andillustrated in FIGS. 1 and 2 is based on the combination of ultra-highkilotesla magnetic fields combined with the non-thermal ignition of HB11fusion reactions using laser pulses of picosecond duration and more than30 petawatts of power, wherein for example 14 mg boron-11 releases anenergy gain of 277 kWh every second. In contrast to the laser-drivendeuterium-tritium nuclear fusion with 2 megajoule laser pulses ofnanosecond duration with the laser NIF with spherical irradiation of 96beams, the HB11 reactor operates with only one beam for non-thermalignition by means of the extremely high, non-linear forces of theelectrodynamic laser field. Relevant measurements at the PALS laserproject in Prague have shown that the non-thermal method yields billionsof times higher energy yields than the classical thermal reaction, whichis in exact agreement with the theory (see [6]).

FIG. 1 shows a schematic illustration of an embodiment of theinvention's nuclear fusion reactor 100, for example according to [1],which comprises a magnetic field device 10 for holding a fusion fuel 1with a magnetic field in a cylindrical reaction chamber 2, a magneticfield pulse laser source 20 for emission of magnetic field laser pulses3 (or: magnetic field-generating laser pulses), a fusion pulse lasersource 30 for emission of fusion laser pulses 4 (or: block fusion laserpulses), an energy converter device 40 (shown dashed) for converting theenergy released from the generated nuclei during nuclear fusion, and aneutron elimination device 50. The nuclear fusion reactor 100 preferablyhas a spherical structure as illustrated in FIG. 3 of [1].

The neutron elimination device 50 with a shielding layer 80 surroundsthe magnetic field device 10 and the energy conversion device 40 on allsides in the form of a predominantly closed housing. The shape of theneutron elimination device 50 can be box-shaped or alternativelyspherical as shown. The neutron elimination device 50 comprises a wallmaterial comprising tin or a tin compound. The thickness of the tin ortin compound is selected in accordance with the operating conditions ofthe nuclear fusion reactor 100. The thickness is preferably selectedsuch that the neutron number is reduced by the effect of the neutronelimination device to a negligible degree, in particular to a degreewhich avoids further nuclear reactions.

The magnetic field device 10 for generating a magnetic field with astrength of e.g. 4.5 kT in reaction chamber 2 comprises two parallelmetal plates 11, 12, which are made of e.g. nickel, have a thickness ofe.g. 2 mm and a characteristic extension of e.g. 3 cm. The metal plates11, 12 are connected by electrical conductors forming two turns 13 of acoil. One of the metal plates 11 has a hole 14 through which themagnetic field laser pulses 3 with a duration of e.g. 1 ns to 2 ns ande.g. 10 kJ energy are irradiated. The plasma generated by each magneticfield laser pulse 3 generates a current pulse in the coils 13 with amagnetic field of a volume of cubic millimeters and a duration ofseveral ns.

The hole 14 is a circular opening in the upper metal plate 11 shown inFIG. 1. The diameter and optionally also the geometrical shape of hole14 are selected depending on the properties, in particular theintensity, diameter and profile of the magnetic field laser pulses 3.For example, the diameter of hole 14 is 5 mm. Deviating from thecircular shape, an elliptical shape can be provided, for example. Thehole 14 can be optimized to maximize the magnetic field for the highestpossible fusion yield.

The second metal plate 12, which is opposite to the hole 14, can beprovided with an absorption layer which serves to reduce the opticalreflection of the magnetic field laser pulses 3 and to increase thedielectric properties of the capacitor formed by the metal plates 11.Preferably, the absorption layer (not shown) is arranged on the entiresurface of the metal plate 12 and is preferably formed of a foammaterial, for example polyethylene. The foam material is selected sothat after laser irradiation an electron density distribution is formedas a double Rayleigh profile.

The magnetic field laser pulses 3 are generated with the magnetic fieldpulse laser source 20 shown schematically, which contains, for example,a Nd-YAG laser and further optical components (not shown) for directingthe magnetic field laser pulses 3 towards the magnetic field device 10.Optionally, the magnetic field laser pulses 3 of a duration in thenanosecond range can be shortened in time by using an iodine laser witha pulse length of 100 ps and/or by shorter laser pulses after CPA powerincrease. Advantageously, the magnetic field generated by the magneticfield device 10 can thus be amplified.

The fusion pulse laser source 30 is configured to generate the fusionlaser pulses 4 with a duration of less than 5 ps and an intensity above10¹⁹ W/cm². The fusion laser pulses 4 preferably have a contrast ratioof at least 10⁶ for a duration of less than 5 ps prior to the arrival ofthe fusion laser pulses 4 on the fusion fuel 1. Furthermore, the fusionlaser pulses 4 preferably have an intensity distribution which exhibitsless than 5% fluctuations over the beam cross-section, except in anouter 5% edge region of the beam cross-section. This is advantageous foroptimizing the block ignition of the fusion reaction in fusion fuel 1.The mentioned intensity distribution is achieved, for example, by afusion pulse laser source 30, which has a bundle of fiber amplifiers,each individual fiber having a single mode emission. Furthermore, thefusion pulse laser source 30 contains a pulsed laser, such as asolid-state pulsed laser, for the generation of ps laser pulses.

The magnetic field pulse laser source 20 and the fusion pulse lasersource 30 are coupled to a control device 70. The control device 70 isconfigured in such a way that the magnetic field laser pulses 3 and thefusion laser pulses 4 are synchronized in time with one another. Inreaction chamber 2, the maximum magnetic field is generated immediatelybefore each of the fusion laser pulses 4 arrives at fusion fuel 1.

The fusion fuel 1 is a solid-state dense, cylindrical body based onHB11, for example with a length of 1 cm and a diameter of 0.2 mm. Thesurface of the fusion fuel 1 carries a cover layer at the laserinteraction area with a thickness of three laser vacuum wavelengths. Thecover layer consists of elements with an atomic weight higher than 100,for example silver. The cover layer improves the pulse transmission forgenerating the fusion flame in fusion fuel 1. The fusion fuel 1 is heldin the magnetic field device by quartz filaments.

The energy converter device 40 generally comprises an electricallyconductive component (shown schematically as a dashed line in FIG. 1,see also FIG. 3), which surrounds the magnetic field device 10 on allsides. The magnetic field device 10 is supported inside the energyconverter device 40 (carrier not shown in FIG. 1, see e.g. carrier bar44 in FIG. 3). The energy converter device 40 is preferably connected toground potential, while a negative high voltage, for example −1.4 MV, isapplied to the magnetic field device 10 by a voltage source 15. Theenergy converter device 40 is arranged to capture high-energy He nuclei(alpha particles) released during the fusion reaction of fusion fuel 1and to convert them into a discharge current by means of voltage directcurrent transmission (HVDC) [1]. The discharge current provides theelectrical energy into which the energy released during the fusionreaction is converted.

In deviation from the illustration in figure, the direction of incidenceof the magnetic field laser pulses 3 can be rotated by an angle of up to80° between perpendicular incidence in the plane defined by theperpendicular incidence direction and the normal of the magnetic field,the rotation being in the plane oriented parallel to the coils 13.

The neutron elimination device 50 may be provided with a thermalizationdevice 60 on its side facing the fusion fuel 1, as shown schematicallyin FIG. 2. The thermalization device 60 contains a thermalizationliquid, such as liquid paraffin.

An HB11 nuclear fusion reactor which is sufficiently clean underpractical conditions can be obtained according to the invention inparticular by making the spherical reactor vessel of the nuclear fusionreactor from pure tin, or—which is fully economically feasible—from tinisotopes 114 or with 115, and the frequent 116. The neutrons originatingfrom nitrogen convert the tin nuclei into clean, stable nuclei with ahigher atomic weight by neutron capture. In order to slow down theneutrons produced from flying too large, thermalization is applied inthe thermalization device 60 (FIG. 2) using an about 10 cm thick liquidof water or of solid paraffin or of paraffin oil. With the further outerjacket of a tin layer of the neutron elimination device 50, the nuclearfusion reactor 100 is then operating as a perfectly sufficient cleanenergy source. With the liquid intermediate layer of the thermalizationdevice 60, also the heat exchange can be conducted, if the energy of thehelium nuclei should be available only by deceleration in the reactorwall and is not possible in preferred manner by energy conversion inelectrostatic fields between the reactor center, in particular thecenter of the sphere, and the reactor wall, in particular the wall ofthe sphere.

For the tests of the nuclear fusion reactor and for the implementationof the development of the reactor components, the very sensitivemeasurement of the neutrons from the formation of the nitrogen nucleican be used, since the measurement of the HB11 reaction is moredifficult and less accurate to handle.

The features of the invention disclosed in the above description,drawings and claims may be relevant to the realization of the inventionin its various forms either individually, in combination or insub-combination.

What is claimed is:
 1. A reactor configured for energy conversion byfusion reactions, comprising: a reactor vessel; a neuron thermalizationdevice containing a thermalization liquid surrounding the reactor vesseland configured to reduce energy of neurons produced in the reactorvessel and provide moderated neurons, wherein the thermalization liquidcontains at least one of protons, deuterons, carbon, oxygen, and oxygencompounds and metallic tin particles of more than nanometer size; and aneutron elimination device surrounding the neuron thermalization device,the neuron elimination device including tin and configured to at leastpartially react the moderated neutrons with the tin.
 2. The reactoraccording to claim 1, wherein the reactor is a laser-driven nuclearfusion reactor configured to operate with hydrogen and boron isotope 11.3. The reactor according to claim 2, further comprising a magnetic fielddevice configured to hold a fusion fuel and to generate a magnetic fieldhaving a field strength greater than or equal to 1 kT in a cylindricalreaction space, a pulsed fusion laser source configured to emit fusionlaser pulses having a pulse duration of less than 10 ps and a powergreater than 1 petawatt and to initiate nuclear fusion in the fusionfuel; and an energy conversion device for converting energy releasedfrom the generated nuclei during nuclear fusion into power plant output,wherein the neutron elimination device is arranged as wall materialsurrounding the neutron thermalization device of the reactor.
 4. Thereactor according to claim 1, wherein the neutron elimination deviceconsists of elemental tin or a tin, compound.
 5. The reactor accordingto claim 1, wherein the neutron thermalization device is additionallyconfigured to absorb thermal energy from the reactor vessel into thethermalization liquid.
 6. A reactor configured for energy conversion byfusion reactions, comprising: a reactor vessel; a neutron thermalizationdevice containing a thermalization liquid surrounding the reactionvessel and configured to reduce energy of neutrons produced in thereactor vessel and provide moderated neutrons; and a neutron eliminationdevice surrounding the neutron thermalization device, the neutronelimination device including tin and configured to at least partiallyreact the moderated neutrons with the tin, wherein the tin includesisotopes 114 to 119 and less than 0.01% of isotopes 112 and
 122. 7. Areactor configured for energy conversion by fusion reactions,comprising: a reactor vessel; a neutron thermalization device containinga thermalization liquid surrounding the reactor vessel and configured toreduce energy of neutrons produced in the reactor vessel and providemoderated neutrons; and a neutron elimination device surrounding theneutron thermalization device, the neutron elimination device includingtin and configured to at least partially react the moderated neutronswith the tin, wherein the tin includes at least at least 99.9% of anisotope selected from 114, 115, and 116 or at least 99.9% of a mixtureof isotopes selected from 114, 115, and 116.